1. Field of the Invention
The invention relates to a signal transmission circuit and method, more particularly to a signal transmission path selection circuit and method for an electronic device.
2. Description of the Related Art
In the design of a conventional mobile phone 2, if the mobile phone 2 is to have both a USB mode for transmitting data, such as audio-visual data, images, text, etc., and an audio mode for transmitting audio signals, such as music, voice, etc., a USB connector 20 having ten pins, such as that schematically shown in FIG. 1, is generally required. The USB connector 20 is connected to a central processing unit 21 of the mobile phone 2, and can be connected to a matching USB connector 30 provided on a computer device 3 such as that shown in FIG. 2, or to a matching USB connector 40 of an external earphone/microphone device 4 such as that shown in FIG. 3. The first five pins of the USB connector 20 are provided for data transmission between the mobile phone 2 and the computer device 3 in the USB mode, whereas the last five pins of the USB connector 20 are provided for audio signal transmission between the mobile phone 2 and the external earphone/microphone device 4 in the audio mode.
However, the USB connector 20 with ten pins has a larger size than a mini USB connector with five pins (not shown), and takes up more space in the mobile phone 2, so that there is less available space in the mobile phone 2. Therefore, if the functions of the USB connector 20 with ten pins can be replaced by the mini USB connector with five pins, the space occupied by the USB connector 20 when disposed in the mobile phone 2 and when connected to a matching device can be reduced.